From the aerodynamic point of view, the external shape of the body of a high performance road vehicle is designed to achieve two objectives (which are often in contrast with each other): minimizing (both by reducing the overall front section and by reducing the aerodynamic penetration coefficient) the running resistance (i.e. minimizing the aerodynamic load component aligned with and opposite to the motion direction) and maximizing the downforce (i.e. maximizing the downward vertical aerodynamic load component).
In order to increase the downforce, the custom of using specific aerodynamic projecting elements is known, which projecting elements are mounted onto the road vehicle body. One of the most common aerodynamic projecting elements is the rear spoiler which is arranged at the rear portion of the vehicle and serves the function of increasing the downforce (i.e. the downward vertical aerodynamic load) which mainly rests on the rear wheels (which are driving wheels in almost all the high performance road vehicles). The rear spoiler may comprise a single centrally arranged fin-shaped support or a pair of laterally arranged fin-shaped supports (a typical solution in free-circulation or commercially available road vehicles) which support at least one horizontally arranged aerodynamic profile or airfoil and which, being impinged by the air, generate the desired lift. The rear spoiler may comprise a single aerodynamic profile (in this case it is referred to as a single-winged rear spoiler) or two, three or more vertically overlapping aerodynamic profiles (in this case it is referred to as a multi-winged rear spoiler).
A particular multi-winged configuration (generally with two or at most three aerodynamic profiles) includes a primary aerodynamic profile (referred to as “main”) which is aerodynamically assisted by other ancillary aerodynamic profiles (referred to as “flaps”), the leading edges of which are located close to the trailing edge of the main aerodynamic profile to be assisted, and in a sequence, to the trailing edges of the following profiles.
If on the one hand the provision of a rear spoiler increases the downforce (positive effect), on the other hand the provision of a rear spoiler also increases the running resistance (which is a normally negative effect, but when braking), and thus the rear spoiler design should always be a compromise between these two diametrically opposite aspects in order to maximize the road vehicle performance.
In on-track driving, a rear spoiler with a high aerodynamic load is an advantage (due to the positive effect of the downforce) at average speeds (i.e. of the order of 180-240 Km/h; 112-150 mph), at which the road vehicle is strongly accelerated/decelerated and/or is driven on a bend or curve (and therefore the road vehicle wheels must transmit a very high longitudinal force and/or transversal force to the ground); on the other hand, a rear spoiler with a high aerodynamic load is a drawback (due to the negative effect of the running resistance) at high speeds (higher than 280-300 Km/h; 174-186 mph), at which the road vehicle performance is directly linked to the minimization of all the running resistance components. Accordingly, a rear spoiler has been proposed which is provided with at least one adjustable aerodynamic profile mounted to be adjusted between a maximum incidence position, for generating the maximum downforce (and thus also the maximum running resistance), which is generally used at average speeds and when braking, and a minimum incidence position for obtaining the minimum downforce (and thus also the minimum running resistance) which is generally used at high speeds.
However, the currently known rear spoilers provided with adjustable aerodynamic profiles have some drawbacks as they are not able to achieve a high aerodynamic efficiency (i.e. maximize the ratio of the downforce obtainable with the “all-closed” aerodynamic profiles to the running resistance obtainable with the “all-open” aerodynamic profiles) and/or require a complex, heavy and cumbersome actuation system.